Decubitus ulcers, commonly known as bed sores, are caused when the capillaries of a patient are occluded by pressure over long periods of time. With most people, the capillaries begin to occlude when the pressure thereagainst reaches about thirty two millimeters of mercury (32 mm of Hg).
A conventional bed having a conventional mattress supplies a pressure of about eighty mm of Hg to the capillaries, and this easily causes capillary occlusion. However, most people spend relatively short periods of time in bed and the capillaries recover during the time spent out of bed so bed sores do not develop. Comatose patients, on the other hand, spend long and unrelieved periods of time in bed and such patients will develop bed sores if not turned periodically.
Waterbeds have been used as hospital beds because the capillaries of a patient floating on a water-filled mattress are subjected to only about eight to twelve mm of Hg. Accordingly, waterbeds prevent bed sores. However, they have met with limited acceptance by health care professionals, because it is very difficult to turn and position patients lying on a waterbed. Moreover, it is difficult to lift a patient from a waterbed, or to deposit a patient thereonto.
Due to the widespread problem of decubitus ulcers, many inventors have turned their attention to flotation therapy beds. For example, a flotation therapy bed is mentioned in 48 Federal Register 53034 and 53051, paragraph 890, 5170, dated Nov. 23, 1983.
Moreover, Reswick U.S. Pat. No. 3,803,647 shows a flotation therapy bed for preventing decubitus ulcers by use of a steel hospital bed on casters having an air mattress on top of a tub for an aqueous supporting fluid. The Reswick design includes a heating unit for the supporting fluid which includes a thermostatically controlled electrical heater located in the fluid.
United Kingdom patent no. 2,154,445 discloses a relatively inexpensive and light-in-weight waterbed having a porous cover and a molded plastic base that rests atop a conventional hospital or domestic bed frame. It also includes a low voltage heater and heater controls. Rand U.S. Pat. No. 2,719,986 is also of interest as an additional representative sample of the large body of art that discloses controls for the air portion of mattresses.
Despite the many advances that have been made in this field, patients continue to get bed sores, even when provided with patented beds. This is largely because health care professionals have rejected waterbeds due to the above-mentioned difficulties which such beds present to the care provider.
There is a need for a waterbed construction that facilitates the handling of patients on such a bed, but the prior art, when considered as a whole in accordance with the requirements of law, neither teaches nor suggests how such a bed could be provided.
Moreover, there are some patients who cannot be left lying flat on their backs. Thus, there is a need for a flotation therapy bed capable of supporting patients in a sitting-up position, but the art contains no developments that suggests how such a bed could be provided.